Plants with desirable characteristics were produced through conventional breeding for thousands of years. This process is time consuming to fully obtain plants with stable expression of the desirable traits. Through the introduction of genetic engineering in plants, genes are introduced into plants using various transformation methods without the need of crossing. Plant genetic engineering has overcome barriers in producing well grown plants or breeding of plants which are not compatible. However, the modification of plants raised concerns in various aspects from the conduct of research involving genetically engineered plants, the materials used for transformation to its potential risks to the environment, ecology and the society. The released of food products derived from genetically engineered plants has since stir controversies in the community and largely sustains international reports and NGOs coalition with consumers group opposing the idea of genetic engineering in plants for improving food nutritions or to solve issues with food security. Once genetically modified plants are released into the environment, there is the potential for ecological bearing, environmental effects and possible gene transfer. Ecological and environmental risks may have been assessed in agreement to biosafety frameworks but the long term impacts are yet to be seen.
Plant Genetic Engineering Principles
Genetic engineering techniques allowed the isolation, cloning, transformation of genes of exogenous gene into plants, providing mechanism for creating genetic modification and diversity. This is also referred as transgenesis where the plants engineered is referred as transgenic. This genetic engineering principles have it advantages at which a desired gene conferring a trait such as herbicides resistance can be isolated and cloned into a plant without carrying alongside thousands other extra genes. Besides, genes from non-sexually compatible with recipients can be introduced via horizontal gene transfer. Two common procedures are used in the introduction of transgenes into plant cells which utilizes usage of disarmed Ti-plasmid carrying transgene in the left and right borders of its T-DNA region, and the biolistic method. Totipotent cells are often being used for transgene insertion for it to be inherited in the germ line and progeny. Selectable markers such as kanamycin resistant gene are usually co-transferred with transgene to discriminate the genetically engineered plants.
Ecology and Plant Genetic Engineering Principles
Ecology is the study of organisms in relation to its environment. As plants are interconnected with the ecological system, a gene introduction which modifies the plant can be expected to have impacts throughout the ecological system. An ecological threat can be said to occur if the presence of the genetically modified plants expressing transgene results in adverse impact on an ecosystem. Whether or not plants are resistant to herbicides or pesticides, not only weed and pests are eliminated, other beneficial living organisms could be eradicated as well. This reduces biodiversity, giving impact to the ecosystem. Genetically engineered plants when release to the environment would become part of the ecological food chain and non-target species could be exposed directly or indirectly to the transgene it carry. The principle of engineering BT Cry gene conferring for Cry endotoxin into corn or maize as bio insecticides against caterpillar of Lepidoptera: Crambidae produces plants with built-in insecticides. How will genetically modified plant affect the non-target species in the ecosystem? On May 20, 1999, a scientific paper published in Nature raised attention to the potential ecological risks caused by genetically engineered plant. John Losey and his colleagues at Cornell University claimed that a variety of transgenic maize expressing Bt toxin pose detrimental effect to the larvae of monarch butterflies. Studies with monarch butterfly caterpillars, Danaus plexippus, suggested monarch butterfly populations would be reduced from feeding on milkweed leaves coated with Bt maize pollen (Jesse & Obrycki 2000, Losey et al. 1999). Follow-up studies, however, indicated that the impact was negligible because of limited exposure and low toxicity of Bt maize pollen to monarch caterpillars (Dively et al. 2004, Hellmich et al. 2001, Sears et al. 2001, Stanley-Horn et al. 2001).
Recently in 2007, Rosi-Marshall and his colleague at Loyola University Chicago reported that toxins in transgenic corn byproducts may affect to the Trichopteran species. Trichopteran (caddisflies) are closely related to lepidopteran and it feed on decaying organic matter of crops. BT corn is usually cultivated nearby to water streams and this exposes the transgenic plants to the habitat of Trichopteran. Headwater streams are also associated with the neighboring terrestrial environment. Crop byproducts from Bt corn such as pollen may contain Bt toxin which may affect non-target species but no extensive studies are done to assess the risks Bt toxin from transgenic plants can impose to aquatic insects non-target species. Due to this, they examine the effects of these materials on stream-dwelling aquatic insects, using Trichopteran as their model organism. Trichopteran feed by scraping biofilms off submerged surfaces thus could consume Bt corn pollen that maybe deposited on the biofilms. In the experiment, caddisfly larvae are fed with non-Bt pollen and Bt pollen in laboratory feeding trials. Laboratory feeding trials showed that consumption of BT corn byproducts reduced the growth and increased mortality of Trichopteran which is the nontarget stream insects. This suggests that non-target species can be affected by the Bt toxin, contradicting with the claim that Bt toxin expressed by Bt gene in corn will only target larvae from Lepidoptera. Lower growth rates and higher mortality of stream caddisflies, as measured in laboratory feeding studies, could potentially reduce secondary production (Benke AC et al, 2006). This may indirectly affect the food chain since Trichopteran is a main prey for aquatic and amphibians predator. In field scale, the effects of Bt toxin to other non-target species may be even significant since in the open, non-target species are exposed widely to the toxin. The significance of these two examples is that although a gene expressing toxin may target a particular species, the closely related species may be indirectly affected as well. This issue should be address in depth to ensure the sustainability of the ecology to maintain balanced ecosystem.
Environment and Plant Genetic Engineering
Environmental issue associated with the design of plant genetic engineering should be given important consideration. Against what standards should the genetically modified plants be assessed for its environmental risk? To date, analysts use sustainable and organic conventional agriculture as standards (Firbank, 2003). Major concern for genetically modified plants is its invasions. Another drawback in plant genetic engineering principle is pests and weeds resistance to pesticides and herbicides. Darwinian evolution process creating diversity occurred in organisms to adapt to changes in their environments over time for survival. Plants are either engineered to be resistant towards herbicides in which case the genetic engineering company itself produces the herbicides or the genetically engineered plant emits insecticides targeting pest. Aaron J. Gassmann and his colleague (2014) reported the field-evolved resistance by western corn rootworm to multiple Bacillus thuringiensis toxins in transgenic maize that are not high dose in Iowa. Millions of acres of U.S. farmland are now also infested by weeds that have become resistant to the herbicide glyphosate. Overuse of Monsanto's "Roundup Ready" trait, engineered to tolerate the herbicide has promoted the accelerated development of resistance in several weed species. Higher concentration of herbicides or toxic herbicides such as 2, 4-D and dicamba are opt as a solution by farmers. As if on cue, agribusiness companies have begun to develop new GE plants engineered to tolerate these higher concentration and toxic herbicide, with no guarantee that the Roundup Ready case will not repeat itself, producing a new wave of resistant weeds.
Potential Gene Flow
Another major concern with regard to genetically engineered plant is the possibility for gene flow to occur. The functional genome is only partially understood, but foreign genes are still introduced. These genetically engineered plants when released are cultivated outdoor, where they cannot be controlled as they can be controlled in the confined lab environment. Genetically engineered plants can self-replicate and transfer transgene to neighboring fields cultivated with non-genetically engineered plant or to its weedy or wild counterparts. Gene flow is a major concern in genetically modified plants or crops especially if the transgene confer traits that enhance the fitness of the transgene recipient in non-beneficial manner. When transgenes escape and express normally in weedy or wild relatives of transgenic plant species, this establish an unwanted population of transgene in the environment. If the transgenes are responsible for resistance to biotic and abiotic stresses (such as disease and insect resistance, drought and salt tolerance, and herbicide resistance) that can significantly enhance the ecological fitness of weedy and wild populations, the escape of these transgenes will probably cause ecological problem producing aggressive weeds which are hard to eradicate. Weedy rice infests several upland crops such as jute, maize, soybean and vegetables, causing general weed problems (Baki et al., 2000). With the present-day fears of weed problems predominantly in rice farming, one of the major concerns is whether the engineered genes in transgenic rice varieties will escape to their wild and weedy relatives through gene flow.
Transgene flow from cultivated rice to its weedy or wild relatives has been reported and a suggestion has been made that transgenic rice hosting genes that can enhance ecological fitness of weedy rice should not be planted in regions where weedy rice is abundant. Chen and colleague at Yeungnam University Korea studied gene flow from rice to its wild and weedy relatives under field condition. The aim of this study was to assess the extent of gene flow between cultivated rice and two of its close relatives under field conditions. Experiments were conducted at two sites in Korea and China to determine gene flow from cultivated rice (Oryza sativa L.) to weedy rice (O. sativa f. spontanea) and common wild rice (O. rufipogon Griff.), respectively, under special field conditions mimicking the natural occurrence of the wild relatives in Asia. Herbicide resistance (bar) and SSR molecular finger printing were used as markers to accurately determine gene flow frequencies from cultivated rice varieties to their wild relatives. This study clearly provides a good example of a simple way to estimate or predict gene flow from transgenic rice to weedy and wild rice species using herbicide-resistant genes and molecular markers. Gene flow was detected in two experiments conducted at different localities where weedy rice or wild rice is found under natural conditions. The experimental data given here clearly indicate the possibility of gene flow from cultivated rice varieties to wild and weedy species, although with different frequencies. The gene flow frequency from cultivated Minghui-63 to wild O. rufipogon in an alternating cultivation model was detected to be approx. 1.1??2.2 %. These frequencies are significantly high in terms of transgene escape if the cultivated transgenic rice varieties are grown in the vicinity of wild rice species. Messeguer et al. (2001) also detected similar amounts of gene flow from transgenic herbicide resistant rice to non-transgenic counterparts, ranging from 0.01 to 0.53 % in their experimental fields in Italy and Spain. Therefore, the outcrossing rate between weedy and cultivated rice in large populations might be more significant than the data observed in this experiment. Rice cultivars cross easily with their related weedy forms (red rice) found in direct-seeded paddy fields and produce viable and fertile hybrids, and the hybridization rates could range from 1.08 to 52.18 % (Langevin et al., 1990). Gene flow could accumulate and increase through generations. If transgenic rice varieties are released into environments where weedy rice occurs abundantly, the transferred alien genes could spread out and accumulate in weedy populations. , it was nonetheless shown that gene flow between the cultivated and weedy rice species definitely exists. If weedy and wild rice species were to receive herbicide-resistant genes, perhaps in addition to other transgenes from cultivated counterparts through gene flow which can significantly enhance the ecological fitness of the weeds, it may eventually produce so-called `super weeds' in rice ecosystems.
How will genetically engineered plant affect the society? Experimental attempt to boost the methionine level in soybeans resulted in health concern if this product is to be released for sale and consumption. A gene from Brazil nuts was introduced into a soybean variety intended for use as animal feed. Introduction of a new gene may lead to the production of a new protein. In this case the new protein caused a life-threatening allergic reaction in people (Beardsley, 1996). Gilles-Eric S??ralini, et al. 2011, concluded that the raw data from all three GMO studies reveal that novel pesticide residues will be present in food and feed and may pose grave health risks to those consuming them. It is a concern because proteins produced from novel gene which is engineered and its expression is changed in engineered plant maybe pose allergenicity
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